     p/Semigroup
     (-mappend [_ sv sv']
       (and sv sv'))
+
     p/Monoid
     (-mempty [_]
       true)))

    p/Semigroup
    (-mappend [_ sv sv']
      (or sv sv'))
    p/Monoid
    (-mempty [_]
      false)))

    p/Semigroup
    (-mappend [_ sv sv']
      (str sv sv'))

    p/Monoid
    (-mempty [_]
      "")))
